The once-thriving sardine population — made famous in John Steinbeck’s novel “Cannery Row” — has taken a nosedive along the West Coast, where regulators are considering a ban on reeling in the tiny bait fish for a third year in a row.

Sardine numbers have plummeted 95 percent since 2006, according to estimates released Friday by the National Marine Fisheries Service. The perilously low numbers give regulators little choice but to again close fishing starting July 1 from Mexico to the Canadian border.

“If the initial estimate for this year remains in place, the fishery will be closed for the third straight year,” said Kerry Griffin, the staff officer for the Pacific Fishery Management Council, which makes policy along the coasts of California, Oregon and Washington. “We all want a healthy ecosystem, sustainable fisheries and healthy coastal communities that depend on fishing opportunities.”

Fishery biologists blamed the collapse on natural fluctuations — which recent sediment studies show have been common throughout history — and changing ocean conditions. Conservationists, however, believe overfishing made a bad situation worse.

“There would have been a decline anyway, but we made the decline worse by continuing to fish,” said Geoffrey Shester, senior scientist for Oceana, an international advocacy group that has been fighting to lower the annual sardine take and implement stricter regulations. “Scientists in the agency warned about a collapse, but the managers of the fishery didn’t pay attention to that and, in fact, took a much higher percentage of the existing stock.”

The 14 voting members of fishery council, which will meet April 10 to discuss the issue, are required by federal law to close ocean fishing if the number of fish do not reach conservation objectives.

Griffin defended management of the fishery, arguing that sardine populations were very high from 2005 through 2007, just before their numbers began to decline. Fishing is allowed under council rules until the population falls below a certain threshold, which didn’t happen until 2015.

“Look, we have this harvest control rule that is quite conservative and protective of the stocks,” Griffin said. “When the numbers fall below the cutoff, we close the fishery.”

The dilemma harkens back to the mid-1950s when the Monterey Bay canneries of Steinbeck fame began failing, mostly as a result of overfishing. Stiff quotas and catch limits required by the federal 1976 Magnuson-Stevens Fishery Conservation and Management Act helped save the sardines.

The population of the tiny epipelagic fish increased throughout the 1990s and Monterey Bay once again became the Bay Area hub of sardine fishing, with a large population also thriving off the coast of San Francisco.

Huge quantities of the nutrient-rich fish were being hauled up at the Channel Islands in Southern California and along the Oregon coast, where fishermen were catching as much as 65 tons a day of the schooling pilchards and bringing in between $10 million and $20 million in annual revenue from sales, Shester said.

The sardine population peaked in 2007, according to the National Oceanic and Atmospheric Administration. But then sardine numbers — which can only be measured using their collective weight — dropped, from 1,037,000 metric tons in 2007 to the estimate of 86,586 metric tons scientists found this year. That’s well below the 150,000 metric ton threshold required for commercial fishing.

“What’s most troubling to me is that you have this clear story where we’ve made the same mistakes we made during the cannery row days, and yet we have the unwillingness of the management bodies to reform and make changes that could have avoided this,” Shester said. “We have to change the way we manage these fish.”

The fishery collapse isn’t isolated to sardines. Anchovies, which thrive in cold water, have also declined over the past decade due largely to fluctuating ocean temperatures and a lack of zooplankton, their food of choice.

The result has been record numbers of starving sea lions washing up on beaches in California over the past few years because there haven’t been enough sardines and anchovies for pups to eat.

Brown pelicans, too, have suffered from mass reproductive failures and are turning up sick and dead in California and Oregon. A 2010 study found that many of the starving and emaciated pelicans are eating worms and other prey inconsistent with their normal diet of anchovies and sardines.

“This does hurt coastal communities,” Griffin said. “Sardine fishermen can typically fish for other stocks like squid, mackerel and anchovy, but when one or more of those stocks is down, the impact is real.”

Despite some efforts, including among local Indian tribes, to promote the scaly creatures as a healthy local delicacy, sardines are mostly sold for bait. The fish are generally frozen in big blocks for use in commercial long-line fishing and for feed at Australian and Japanese blue fin tuna farms.